Wood chips, pins and fibre produced for example by chipping logs, are largely used in pulp mills for producing paper products. (Material produced from log chipping and the like, although commonly identified by such terms as pins, pin chips, fibre, wood chips etc. will hereafter be encompassed in the collective use of the term "wood chips".) As a first stage in this paper producing process, the wood chips are cooked in a controlled manner to break down the wood fibres. This creates the pulp batter that forms the basic material for the paper.
The cooking stage is very important to the process of making paper products. It is not desirable to either overcook or undercook the chips. It takes longer to cook a large chip then it does a smaller one. Thus an intermixture of large and small chips (including "sawdust" size particles) will result in either an undercooking of the larger chips, or an overcooking of the smaller chips (or more likely a little of both). Thus it is highly desirable to separate the chips by size so that the cooking procedure can be tailored to the specific size of chip and thereby avoid undercooking or overcooking.